Terminal bank



Dec. 21, 1943- c. w. MCWILLIAMS TERMINAL BANK Filed Deal 3, 1941 2 Sheets-Sheet l INSULATION RM m M T NM .A WW N 6 W c Dec. 21, 1943. c. w. McWlLLIAMS TERMINAL BANK Filed Dec. 5, 1941 1 2 Sheets-Sheet 2 INVENTOR ByCI W MC W/LL/AMS ATTOF Patented Dec. 21, 1943 TERMINAL BANK Charles W. McWilliams, Kearny, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 3, 1941, Serial N0. 421,422

3 Claims.

This invention relates to terminal banks and more particularly to terminal banks which are adapted for use with automatic switches of the panel type extensively used in automatic telephone exchange systems. Its principal object is to provide an improved bank of the above type which is simple to construct and easy to maintain and the terminals of which are uniformly and properly spaced and protected against sagging, separation and warping. To this end, a structure is formed of alternate superimposed metal terminal strips and insulating strips, the latter preferably of a hard insulating material, both the metal and insulating strips being stacked within a frame suitably adapted to secure the stack. A compression spring disposed between the uppermost insulating strip of the stack and a cross member secured to the top of the frame exerts, at all times, a moderate clamping pressure upon the stacked assembly in order to take up any slack that may result from the shrinking or warping of the insulation members thereof.

In the construction of terminal banks of the above type it has been the practice heretofore to use as insulating spacers a paper impregnated with an asphaltum compound, and the superimposed structure of strips and spacers is then placed under heat in a mechanism that compresses the bank to size, an operation during which the insulating compound is softened to produce a homogeneous, infusible, insoluble and very rigid structure. It has been found, however, that a terminal bank constructed in this way is liable, in time, to deteriorate and its usefulness to become impaired as a result of the settling, warping and separation of the various insulating layers. Moreover, in repairing a damaged bank constructed as above, say to remove a broken terminal strip, considerable difiiculty is experienced and considerable expense is involved in separating the terminal from the insulating strips, it being usually necessary to ship the bank to the factory and there subject it to heat and very often chemical solvents in order toseparat the spacers and terminal strips lying on top of the defective strip to be removed.

In my proposed terminal bank, two U-shaped vertical member are welded or otherwise rigidly secured to a suitable base with their channels facing each other, and a number of insulated guide rods are afiixed to the base in spaced relation. In the space formed between the channels, alternate layers of insulating and terminal strips provided with apertures to pass through the rods are arranged in a stack. A crossbar is then fitted across the top of the vertical members to form, with said members and the base, a closed quadrilateral clamp that encloses the terminal stack. Between the underside of the crossbars and the uppermost insulation strip or the stack is inserted a compression spring of suitable design that exerts a moderate pressure permanently upon the stacked assembly, which insures its stability against any swelling or shrinking of the insulating strips interposed between the terminal strips.

A terminal bank constructed in the manner briefly described above has a number of advantages. First of all, by eliminating the compression and heating teps required in the manufacture of the conventional bank, the cost of manufacturing the bank is appreciably reduced and, second, the repair of the bank is considerably facilitated by the fact that successive insulation and terminal strips, not adhering to each other, may be easily pulled out of the stack by simply removing the top crossbar and the spring thereunder.

The above and other objects of the invention are fully set forth in the following description and claims, and will be more readily understood by reference to the accompanying drawings in which:

Fig. 1 is a front elevation of the terminal bank, foreshortened lengthwise by the removal of the central portion thereof with the top portion exploded to show more fully the relative position of the different insulating and terminal strips, and the position of the compression spring in relation to the stacked terminal assembly and the top crossbar;

Fig. 2 is a section taken along the section line 2-2 of Fig. l exposing to view an insulating strip, the protruding terminal projections and wiring lugs of the terminal strips showing thereunder;

Fig. 3 shows a portion of one of the terminal strips directly underneath the insulation strip shown in Fig. 2 and lying upon another insulation strip directly beneath;

Fig. 4 is a perspective exploded view of the top portion of the near end of the bank showing the manner in which the strips are stacked and the manner in which the compression pring and the crossbar are disposed thereon, and

Fig. 5 shows the dissociated parts of Fig. 4 assembled and fitted as the upper near portion of the bank.

The terminal bank of my invention comprises an appropriate number of superimposed layers of insulation strips I of any suitable insulating medium such as, for instance, hard sheet rubber, substantially rectangular in shape with regularly spaced holes provided therein, and interposing terminal strips 2 a portion of one of which is shown in detail in Fig. 3. The terminal strips, which may be readily stamped by a punch press, each have a plurality of regularly spaced projections 3 in opposite sides to serve as terminals to be engaged by movable brushes or other contact members having access to either side of the bank.

These projections 3 are spaced differently for. three groups of strips (ii the terminal bank is to serve for a movable brush equipped with three contact making elements). The strips of one group which is to serve as the tip terminal row will have their projections 33, regularly spaced, in accordance with the separation to be provided between the difierent brushes, but the projection that will be accessible to the "tip centact element of the brush at the extreme left of the banli will, of course, be nearest to the closest of the wiring lugs 3. Iloe strips of the second group of terminals which is to serve as the sleeve terminal row will have their projections 3 regularly spaced as above, but the projection which will be accessible to the contact element (or elements) of the sleeve brush at the extreme left of the bank will be to the right of and adjacent to the projection reserved for the tip. The strips of the third group of terminals which is to serve as the ring terminal row will also have their projections? regularly spaced as above, but the projection whichwill be accessible to the contact element of the ring brush at the extreme left of the bank will be to the right of and adjacent to the projection reserved for the sleeve. Corre sponding projections on the same strips are correspondingly spaced to preserve the same relative distance for all groups of projections when a strip fromeach group is stacked one upon the other "in the orderrequired to present terminal exposure to the selecting brushes having access thereto.

Each metal terminal strip 2 is provided with a wiring lug 4 at either end for the connection of Wires thereto, and the strips are further previded with suitable openings} which align with openings 5 of the insulating strips when both insulat ing and terminalstrips are alternately stacked one upon the otheri The terminal strips may also have other openings, such as openings 8 forexample, to reduce their body and their electrostatic capacity;

The strips I and 2, in the required number to form a bank, are assembled in superimposed relation within a frame 9, the latter comprising a base H] to which is welded or otherwise secured at the ends thereof two U-shaped inwardly facing channel members I i, said members being suitably bolted to a floor supporting member I2. The base It is provided with a suitable number oi'openings through which pass the upright endthreaded rods I, each enclosed by an insulating bushing I3. The holes 5 and 6 or" the insulating and terminal strips I and 2, respectively, have a slightly larger diameter than the diameter of a bushing 53- and are so located that when the strips are stacked within the frame, the bushings (as well as the enclosed rods) will pass through the aligned holes. The rods I are tightly secured to the base It by nuts I i and are held in tightened position by interposed lock-washers I5. The inner sides oieach of the channelmembers II are lined with formed insulation I8 which extends to the base it! and is of a thickness that leaves a rectangular groove sufiiciently wide for the ends of the strips to slide therethrough.

In stacking the strips, an insulation strip I is positioned atop of the channels I I between the grooves thereof and passes over the bushings I3 until it comes to rest on the upper surface of the .base IE). This is followed by one of the terminal strips 2 which, or" course, will come to rest upon the insulating strip beneath it. The next strip will be an insulating strip which is followed, in turn, by a terminal strip. Thus alternate insulating and terminal strips are stacked one upon the other between the two grooves formed by the upright channel members II, and when the desired numbers of strips I and 2 are stacked within the. frame 9, a compression spring I I is placed upon the stack. This spring may be of any shape but preferably corrugated in form, with a length and width substantially equal to those of an insulating strip I and provided with openings 28 which, when the spring lies ontop of the terminal stack, align with the openings 5 and 6 cf the insulating and terminal strips, respectively, to permit the passage therethrough of the insulated bushings I3 and the enclosed rods I. The spring is then compressed into a position that will exert a moderate pressure upon the stacked as sembly by the clamping cross member I6 which is r cta lar n e-pa o a n th at will cause it te be supported on top of the channel members I and provided with regularly spaced openi n gs It which are aligned with opening 6, 5 and 215 for the passage of the insulated bushings I 3 and the enclosed rods {the length of each bushing being suiiicient to cause the upper end thereof 50. just clear the upper surface of the. clamping cross member I6 and, cause thereby the upper threaded ends of the rods, I to protrude thereover. The cross member i6 is then tightened into position by the nuts I l threading over the rods and held in a tightened position by the interposed lock-washers I5, as shown in Fig. 5.

The spring I 'I exerts a moderate clamping pressure upon the entire terminal stack and thereby insures stability of assembly by preventing any lateral or sideway displacement of the terminal strips 2 should the insulating strips I shrink or warp, If the spring I? were not provided and the n ulatin strips should shrink, then, although the terminal stack might originally be tight-fitted under the clamping cross member It When first assembled, yet any shrinking or swelling; of the insulation, strips that might occur thereafter would loosen the terminal strips, cause them to move ideways by the slackness or pressure and thereby cause them tolose. their vertical alignment. Hence by, providing a compression spr g be ween the underside of the crossbar Is and the 9D, of the terminal stack, a moderate pressure is applied to the stack that will counteract the effect of any change in. the, insulating strips, 7

Ir it is necessary to remove a defective insulating or terminal strip andreplace the same by a new one, it is only. necessaryto lift the cross member I6 and spring, I'I. oh? the stack by removing the upper nuts I A and lock-washers I5 and lift out of the stack, the pile of insulating.

and terminal strips resting upon thestrip. to be removed and replaced. The new strip. is then mi f dai fihe Po ti n pre ious oc pied by the s esti e. on nd all, he othe p ap ro- PI te na n are th n aQ d upo t n the manner described, after which the spring I! and cross member iii are fitted to the top of the stack and tightened into position by the nuts 4.

While I have described my invention in connection with its specific application to a particular type of terminal bank, it is to be understood that various other application and embodiments thereof may be made by those skilled in the art without departing from the spirit of the invention as defined within the scope of the appended claims.

What is claimed is:

1. A terminal bank comprising in combination a base, two upright U-shaped members supported upon said base one at each end thereof with the channels of said member facing each other, a plurality of formed terminal strips and insulating strips disposed in alteration for slidable insertion within the channels of said U-shaped members to form a stack, and yieldable clamping means secured to the top of said U-shaped members for holding the stack in a condition of stability.

2. A terminal bank comprising in combination a base, two upright U-shaped members supported upon said base one at each end thereof with the channels of said members facing each other, a plurality of formed terminal strips and insulating strip disposed in alternation for slidable insertion within the channels of said U-shaped members to form a tack, clamping means secured to the top of said U-shaped members, and means interposed between said clamping means and the top of said stack for exerting a pressure on said terminal stack in the stacking direction to maintain the stability of the stack.

3. A terminal bank comprising in combination a base, two upright U-shaped members supported upon said base one at each end thereof with the channels of said members facing each other, a plurality of rods having threaded ends secured to said base, sleeves of insulating material surrounding said rods, a plurality of formed terminal strips and insulating strips arranged in alternation, each of said strips being provided with openings for the passage of said rods therethrough and each adapted for slidable insertion within the channels of said U-shaped members to form a terminal stack, a clamping cross member supported on the top of said U-shaped member and provided with openings for the passage therethrough of threaded portions of said rods, a compression spring having openings for the passage therethrough of said rods, said compression spring being disposed between the top of said terminal stack and the under-surface of said clamping cross member, and nuts threaded to said rods for holding said clamping cross memher in position whereby said compression spring exerts a pressure on said terminal stack in the stacking direction.

CHARLES W. McWILLIAMS. 

